import java.util.Scanner;

public class Homework0324fifth {
    public static void main(String[] args){
        System.out.println("请输入成绩x=:" );
        Scanner sc = new Scanner(System.in);
        int x=sc.nextInt();
        if(x<0||x>100){
            System.out.println("您输入格式有误，请重新输入！");
        }
        else if(x>0&&x<60){
            System.out.println("C");
        }
        else if(x>=60&&x<80){
            System.out.println("B");
        }
        else{
            System.out.println("A");
        }

    }
}
